Abrasive polishing suspensions and method for making same

ABSTRACT

THIS INVENTION RELATES TO A PERMANENT SUSPENSION OF ABRASIVE POLISHING POWDERS. THE SUSPENSION MEDIA CONSISTS ESSENTIALLY OF A GLYCOL BASE THICKENED BY A NEUTRALIZED CARBOXY POLYMETHYLENE POLYMER.

Us. or. 51-298 ABSTRACT on THE DISCLOSURE This invention relates to a permanent suspension of abrasive polishing powders. The suspension media consists essentially of a glycol base thickened by a neutralized carboxy polymethylene polymer.

. This invention relates to abrasive polishing suspensions and, more particularly, to permanent suspensions of powdered abrasive materials in a nonaqueous or partially aqueous glycol base.

Abrasive polishing materials have been suspended in various water base solutions. These presently available suspensions are not permanent suspensions because the abrasive particles will settle out and cake at the bottom of the container. Further, water base suspensions have a high evaporation rate which requires periodic additions of fluid to maintain the properties of the polishing compound while on a lap.

It now has been'discovered that permanent suspensions of abrasive polishing powder can be achieved by utilizing a suspension media which contains non-aqueous or partially aqueous glycol.

In accordance with the invention, it has been discovered that the glycol base suspension media can be made to permanently suspend abrasive powdered particles so that they will not settle out or cake at the bottom of the container as is the case with presently available metallographic and semi-conductor polishing formulations. Further, the suspending media has anti-drying properties due to the low vapor pressure of the glycol base. The evaporamm rate is minimized and periodic additions of fluid are not required to maintain the properties of the polishing compound While on the lap. Another factor contributing to the anti-drying properties, of the suspensions of the present invention, is the high hygroscopicity of the glycol family of compounds. For example, at 80 F. and 60% relatively humidity a 50% aqueous solution of ethylene glycol would lose through evaporation a maximum of of its water.

'Another advantageof the suspensions of this invention is that glycol base suspensions are completely soluble in water and are soluble in many organic materials normally insoluble in Water. This is an advantage over oil based lapping compounds. Further, suspensions made from glycol based formulations have a much broader useful temperature range. A' pure ethylene glycol base would be liquid from 12 C. to 200 C., over twice the range of pure water. Also, since glycols reduce surface tension in aqueous systems, they provide superior wetting properties by their presence in the polishing suspensions.

Accordingly, the present invention is predicated on the use of various glycols such as ethylene glycol, diethylene glycol and triethylene glycol, but preferably ethylene glycol alone or in combination with each other and/or water. To the glycol base is added a carboxy polymethylene polymer of high molecular weight to thicken the suspension and produce a permanent suspension of abrasive particles in the glycol or glycol water base. Suspensions made according to the invention have a shelf life exceeding one yearwithout settling of abrasive powder particles.

3,817,727 Patented June 18, 1974 ice Any polishing agent can be suspended by the method of this invention. Typical powders are aluminum oxide powders having an unagglomerated average of particle size in the range of from about .05 to 1.0 microns, sold by Union Carbide Corporation under the trade name'Linde Type A, B or C. Other powders could be, for example,

' silicon carbide, beach sand, etc. Suspensions of these and other powders will be illustrated in the example given herein below by way of illustrating the scope and spirit of the invention. 9 Y J According to the invention, the suspensions are made by blending a carboxy polymethylene polymer of high molecular weight, such as the type sold by B. F. Goodrich Chemical Co. under the trade name Carbopol 941 into ethylene glycol. The Carbopol 941 is supplied as dry, fluflz'y powders in acid form requiring neutralization to develop optimum properties. Carbopol 941, as described in Service Bulletin GC36 (Revised) of The B. F. Goodrich Chemical Company, is a commercially available water-soluble carboxy vinyl polymer resin having the following properties Physical properties Appearance: Flufly, white acid powder Bulk density: 13 pounds per cubic foot (approximate) Specific gravity: 1.41 Moisture content as shipped: 2% maximum Equilibrium moisture content, room temperature, at

relative humidity: 8% pH of 1% water solution: 3

Z thickened by a neutralized carboxy polymethylene polymer.

Having described the invention in general terms, the following examples are provided to illustrate the various forms the invention may take and the methods for achieving the permanent suspensions of the invention:

EXAMPLE I 1.0 gram of Carbopol 941 resin was blended into 400 cc. ethylene glycol. After allowing the mixture to soak for several minutes, 10 cc. of a 25% aqueous solution of diisopropanolamine was blended with the Carbopol/ glycol mixture to neutralize the Carbopol and form a thick mucilage. In another blender 150 grams of Linde A (0.3a) alumina polishing powder was dispersed in another 400 cc. of ethylene glycol. Twenty drops ofred dye were added for coloring. This alumina dispersion was quickly poured into the previously prepared Carbopol mucilage in the first blender and thoroughly blended into the mucilage. A permanent pink suspension of Linde A in ethylene glycol resulted. The composition of the suspension was as follows:

Weight percent Ethylene glycol 84.6

Power 14.3

Carbopol 0.1

25 aqueous solution of diisopropanolamine 1.0

EXAMPLE H Identical procedure to Example I, except that grams of Linde C (1.0 4) alumina polishing powder were vs diai a 9t L d a and. of the red dye. A permanent yellow suspension of Linde C resulted.

EXAMPLE III 1.0 gram of Carbopol 941 resin was blended with 400 cc. of ethylene glycol- After allowing mixture to soak for several .minutes, 10 cc. of 25 aqueous solutionof diisopropanolamine was blended into the Carbopol/ glycol mixture to neutralize the Carbopol and form a thick mucilage. In another blender 150 grams of Linde A alumina powder were dispersed in 400 cc. of water. Twenty drops of red dye were added to this dispersion. The alumina/water mixture was quickly transferred to the Carbopol mucilage in the first blender and thoroughly blended with the mucilage. A permanent pink suspension of Linde A'in a water/glycol base resulted. The composition of the suspension was'as follows:

. Weight percent Ethylene glycol 44.1 Water 40.0 Powder 14.8 Carbopol 0.1 25% aqueous solution of diisopropanolamine 1.0

EXAMPLE IV Identical procedure to Example II I except Linde C alumina powder and yellow dye were used in place of Linde A and red dye. A permanent yellow suspension of Linde C resulted. EXAMPLE V Identical procedure to Example III, except l QOgrams of Linde B (0.05m alumina polishing powder and blue dye were used inplace of Linde A and red dye. A per-- manent blue suspension of Linde B resulted.

EXAMPLE VI Identical ingredients and procedure to Example V, except that 4.0 cc. of a 10% aqueous NaOH solution were used to neutralize Carbopol instead of diisopropanolamine.

' EXAMPLE VII 21 grams of Carbopol 941 were dispersed in one quart of deionized water. This unneutralized Carbopol mucilage was then blended into two gallons of ethylene glycol in a 24 quart steel tank with a ,6 hp. model 8A Eastern mixer with a 5 /2" diameter propeller running at 725 r.p.m. In a separate 12 quart tank, 6% lbs. of Linde C powder were dispersed in two gallons of deionized water using a hp. model SVA Eastern mixer with a 3" diameter propeller. 15 cc. of yellow dye were added to this mixture. The ethylene glycol/carbopol mixture in the large tank was then neutralized with 200 cc. of aqueous diisopropanolamine. The Linde C dispersion was then added quickly to the large tank containing the mucilage and the entire mixture was blended to 10-15 minutes using the Model 8A Eastern mixer previously mentioned.

A permanent yellow suspension of Linde C in a glycol/ water base resulted. This example demonstrates the adaptability of this process to production scale batches.

EXAMPLE VHI Same procedure and ingredients as used in Example III except Corundum 1600 abrasive powder was suspended in place of the Linde A. Corundum 1600 is manufactured by Bausch & Lombe and has a mean particle size of approximately 10 microns. It is used extensively in the manufacture of ophthalmic lens.

EXAMPLE 1X Same procedure and ingredients as used in Example III, except Corundum 1000 Bausch and Lombe) abrasive powder was suspended in place of Linde A. This abrasive has a mean particle size of approximately 18 microns.

is w d awasusedinplace Same procedure and ingredients as used in Example EIII, except TAM Zirox B'abrasi-ve (Zirconium oxide) was suspended in place of Linde A. This polishing abrasive ha ,amai mum. P5 iz micrq sap is used'in precision glass and mineral-polishing EXAMPLE XI- q Same procedure andingredients as usedin #Example III, except Norton No. 320 SiCabrasive 'was suspended in p1ace of Linde A. This material has;a mean particle size of 32 microns.

E AM LEX IT Same procedure and ingredients as used in Example III, Nonbide NOI'3Z0B C abrasive was suspended in place of Linde A. This material has a mean particle size" of32 microns. EXAMPLE XIII Same procedure and'ingredients as used in Example III, except spheroidizedalumina-having a particle-size range from 74 to' 44 microns'was suspended in'place of' LindeA. 5

EXAMPLE XIV Same procedure and ingredients as used in Example- III, except SiO (Kona sand) having a particle size. range of 74 to 60 microns was suspended in-place of- Linde A.

EXAMPLEXV- 1 Same procedure and ingredients as used in Example III, except jewelers-rouge polishing compound used in place of Linde A. 1 v I EXAMPLE XVI Ethylene glycol 54.64 Powder 27.70 Water 17.23 Carbopol 0.12 e 25% aqueous solution of diis'opropanolamine 0.30

1.0 gram of Carbopol 941 resin was blended into 400 cc. of propylene glycol. After allowing mixture to soak for several minutes, 10 cc. of 25% aqueoussolution of diisopropanolamine was blended into the Carbopol/ glycol mixture to neutralize the Carbopol and form athick mucilage. In another blender grams of Linde C (1.0 4) alumina powder were dispersed in 400 cc. of water. Twenty drops of yellow dye were added to this "dispersion. A

The alumina/water mixture was quickly transferred to the Carbopol mucilage in the first blender and thoroughly blended with the mucilage. A permanent yellow suspension of- Linde C in awater/propylene glycol base resulted.

EXAMPLE XVIII Identical procedure to Example XVII except that dipropylene glycol was used in place of propylene glycol.

EXAMPLE XIX Identical procedure to Example XVII except that dicthylene glycol was used in place of propylene glycol.

EXAMPLE XX Identical to Example XVII except that triethylene glycol was used in place of propylene glycol.

EXAMPLE XIX Identical to Example XVII except that tetraethylene glycol was used in place of propylene glycol.

EXAMPLE XXII Identical to Example XVII except that hexylene glycol was used in place of propylene glycol.

EXAMPLE XXIII 1.0 gram of Carbopol 941 resin blended into 400 cc. propylene glycol. After allowing the mixture to soak for several minutes, cc. of a 25% aqueous solution of diisopropanolamine was blended with the Carbopol/ glycol mixture to neutralize the Carbopol and form a thick mucilage. In another blender 150 grams of Linde C (1.0a) alumina polishing powder was dispersed in another 400 cc. of propylene glycol. Twenty drops of yellow dye were added for coloring. This alumina dispersion was quickly poured into the previously prepared Carbopol mucilage in the first blender and thoroughly blended into the mucilage. A permanent yellow suspension of Linde C in propylene glycol resulted.

Example I and XXIII illustrate the use of two nonaqueous glycol formulations using the lowest molecular weight members of two families of glycols, the ethylene glycols and propylene glycols. Examples XIX through XXI illustrate the use of higher order ethylene glycols in a water/ glycol formulation. It is a reasonable assumption that the higher molecular weight polyethylene glycols of the form HOCH (CH -O-CH ),,CI-I -OH would form successful suspensions, both aqueous and non-aqueous, for higher values of n than have been attempted in the examples listed. This would especially be true for n up to 7, which glycols are still liquid at ambient conditions.

Examples HI through V are the preferred formulations of this invention.

All of the previous examples have utilized only a slight excess of neutralizing agent leaving the suspensions in a neutral or slightly alkaline invironment with pH lower than 10. All of the neutralizing agents for Car-bopol resins are bases, either organic such as diisopropanolamine used throughout most of the examples, or inorganic such as NaOH in Example VI. Other bases which will neutralize Carbopol resins in the ethylene glycol/water system are ammonium hydroxide, triethanolamine, monoethanolamine, triethylamine, and Ethomeen C-25. Diisopropanolamine has been found to be the most eflicient neutralizing agent in the present systems and is the preferred agent. An advantage of the suspensions made using this preferred organic base is that there are no inorganic ions, such as Na, present to any extent. Ions such as sodium are very deleterious to polished semi-conductor substrates.

For some applications, however, it is advantageous to have either a high or low pH or an ionic system. The properties of the Carbopol suspension are'unatfected over a pH range of 3 to 12, however, the adjustment of pH and addition of inorganic additives must be made after the Carbopol has been neutralized completely with the neutralizing agent.

The Carbopol 941 is preferred in these formulations over the other Carbopol resins due to its ability to form relatively low viscosities in ionic systems. The other Carbopol resins are used to provide much thicker emulsions and suspensions.

Applications for these alumina suspensions are as widespread as the powders from which they are formed. They can be used in essentially all polishing operations which now use the alumina powders, with the new advantage of being easier to handle than the powder counterpart. Being viscous, they remain on the laps longer than a similar water slurry, and they are much less susceptible to drying on the lap. Since they are chemically neutral, they will not corrode laps as will some of the other formulations on the market.

What is claimed is:

1. A polishing composition consisting essentially of an abrasive polishing powder having an unagglomerated particle size of from about .01 to about microns suspended in a media consisting essentially of a glycol thickened by a neutralized carboxy polymethylene polymer.

2. A composition according to claim 1 wherein said media consists essentially of ethylene glycol thickened by a neutralized carboxy polymethylene polymer and up to 50% by weight water.

3. A composition according to claim 1 wherein said carboxy polymethylene polymer is neutralized by a base material taken from the class consisting of ammonium hydroxide, sodium hydroxide and organic amines.

4. A polishing composition consisting essentially of alumina powder having an unagglomerated average particle size of from .05 to 1.0 micron suspended in a media consisting essentially of ethylene glycol thickened by a neutralized carboxy polymethylene polymer and up to 50% by weight water.

5. A permanent polishing composition suspension consisting essentially of about 84.6 percent wt.-percent ethylene glycol, about 14.3 wt.-percent alumina polishing powder, about 0.1 wt.-percent carboxy polymethylene polymer of high molecular weight and about 1.0 wt.-percent of a 25 aqueous solution of diisopropanolamine.

6. A permanent polishing composition suspension consisting essentially of about 44.1 wt.-percent ethylene glycol, 40 wt.-percent water, 14.8 wt.-percent alumina powder, about 0.10 wt.-percent carboxy polymethylene polymer and about 1.0 wt.-percent of a 25% aqueous solution of diisopropanolamine.

References Cited UNITED STATES PATENTS 2,375,823 5/1945 Saunders 51308 3,170,273 2/1965 Walsh et al. 51-308 3,715,842 2/1973 Tredinnick et al. 51308 DONALD J. ARNOLD, Primary Examiner U.S.C1. X.R. 

